Statistical Evaluation of BMP Effectiveness in Reducing Fecal Coliform Impairment in Mermentau River Basin

Abstract

This paper presents a statistical method for determining pathogen sources and for evaluating the effectiveness of conventional Best Management Practices (BMPs) in reducing fecal coliform bacterial impairment using water quality data monitored from 1980 – 2006 in the Mermentau River Basin. The statistical method mainly involves (1) determination of seasonal variations in the mean of flow and fecal coliform count in order to identify critical months of pathogen pollution, (2) establishment of multiple correlations between fecal coliform count and rainfall and other solid or sediment-related water quality parameters, (3) detection of temporal variation trends in the median of fecal coliform count in different watersheds within the basin, and (4) evaluation of the effectiveness of BMPs in reducing fecal coliform bacterial impairment based on the trend analysis and water quality criteria. Results of the statistical evaluation show that (1) February – May are the critical months of the highest fecal coliform count; (2) The main pollution in February – March is caused by wet weather runoff; (3) The severe pollution in April and May is related to the releases of muddy rice_field water; (4) Since the implementation of BMPs in 1990, water quality in most watersheds in the Mermentau River Basin has shown an improving trend in terms of fecal coliform count while it was worsening from 1980 – 1990. In terms of pathogen impairment the most polluted areas in the basin are the two watersheds Bayou Queue de Tortue and Bayou Plaquemine Brule, followed by the Bayou Nezpique watershed; and (5) BMPs need to be enhanced in the basin to meet water quality standards.